I’ve been a bit of a lunatic about the moon this winter. Its bright fullness through my unadorned windows, especially “on the breast of the new-fallen snow,” contributed to a somewhat maddening sleeplessness on more nights than just the one before Christmas. Sometimes I met my insomnia with bouts of cleaning, sometimes with yoga, but often with language, my favorite companion when my household is asleep. I found the rituals of dusting and wiping, stretching and breathing, and reading, writing, and questioning language to be comforting and soothing in the wee hours. I figured that because the moon was keeping me up — and might do so a couple nights a month through the winter — I might as well learn more about it in the cozy hibernacle of my study.

While the winter of 2010-2011 has been a rough one for weather (thundersnow!) and geological events (tsunami!), it’s been good for astronomers and philologists alike. It began with an eclipse on the first day of the northern winter, December 21st, a rare, red-mooned spectacle that kept people up into the wee hours hoping to catch a glimpse. And now, as I finish writing this entry, on winter’s last day, March 19th, the moon is rising out my window, nearer to the earth than it’s been in eighteen years, and will appear larger and brighter in the night sky than usual.

Besides their exceptional visuals, both of these events have wonderful orthographic treasures waiting to be explored: a lunar eclipse on the winter solstice and the perigee moon on the eve of the vernal equinox are full of fancy words just waiting to be unpacked. The solstices mark the beginnings of winter and of summer, when the sun (<sol>) appears to stand still (<stice>, as in armistice). The vernal (spring) and autumnal equinoxes are marked by equal (<equ>) hours of both day and night (<nox>). As the sun guides our seasons, the moon guides our months. So, equipped with our standard investigatory tools, this column is dedicated to our nighttime satellite, the moon, and the words we use to understand it, in hopes that it can shed a little light on the patterns that guide our lives and on those that guide our writing system.

The first of these hibernal events captures the Latinate forms for both the nocturnal and diurnal orbs in lunar and solstice respectively. The adjective derives from the Latin luna, ‘moon,’ also the name of the Roman moon goddess, Luna (Selene in Greek). A quick word search on morewords.com reveals the astronautical terms perilune and apolune, meaning ‘close to / far from the moon’ respectively. These words suggest a base of <lune> rather than *<lun>, as do the words lunette (‘little moon’), demilune (‘half-moon’), and lunate, all connoting crescent shapes. But the moon isn’t all outer space and pretty shapes: it has also been long associated with madness. Moon-induced sleepwalking, or lunambulism, has been blamed for lunacy. While the Latin word lūnāticus originally meant ‘moon-dweller’, by the time it made it into English, via French, as lunatic, it already referred to periodic insanity, the waning moods and waxing madness blamed on the phases of the moon.

Of course, the Romans weren’t the only culture to associate the moon with insanity; the concept was likely a calque from ancient Greek, in which moonstruck manics were called selenobletos. According to etymonline, the New Testament Greek word for ‘epileptic,’ mistakenly thought to be a mental illness, was seleniazomai — remember the moon goddess Selene? Compare selenology, the scientific study of the moon, or selenography, lunar map-making, what geography is to the Earth. The OEDlists a couple dozen selenic relatives, including my favorite, selenotrope, a plant that turns toward the moon.

In Modern English, the word moon retains several senses of madness: over the moon means crazily happy; to moon over someone is to pine obsessively, and to moon about means to loaf or mope depressively. Someone who is foolishly daydreamy may be called moony or moonstruck, and both moonshine and moonlighting have criminal origins. To ask for, reach for, or promise the moon is to expect the insanely impossible, and to think someone hung the moon is to give him mad credit. The English association of selenicism and insanity dates all the way back to the earthy Anglo-Saxons: etymonline informs us that the Old English word for ‘lunatic’ was the compound monseoc, ‘moonsick,’ and periodic ‘lunacy’ was mona­ð­seocnes, or ‘monthsickness.’

Here we see that the moonis not only associated with madness, but also with months. Moon and month are obviously related conceptually, but what about orthographically? They cannot be morphologically related, since they don’t share a base, but they are clearly etymologically related. While the Modern English words don’t share a base, the Old English words did: mon or mona meant ‘moon’, and it was suffixed to form monað, ‘month.’ The Old English suffix <-að> (also spelled <-aþ>) is just one of several word suffix spellings that merged into the Modern English <-th> suffix, which forms nouns from either verbs, as in growth, stealth, and health, or from adjectives, as in dearth (<dear> + <th>, ‘scarcity, dearness’)or warmth. But in addition to affixing to free base words that themselves have inherent grammatical categories (or parts of speech), the nominal <-th> suffix more frequently applies to bound bases that have free cognates, as in birth (see bear), depth (see deep), strength (see strong), and breadth (see broad). The word month is just such a construction: the <-th> suffix affixes to the bound base <mon>, meaning ‘moon,’ which is also seen in the proper noun <Monday>, a compound just like its calendrical predecessor <Sunday>.

John Ayto’s Dictionary of Word Origins tells us that the “Indo-European [base] *mēnes- meant both ‘moon’ and ‘month.'” This reconstructed historical base gave us the Latin mensis, ‘month,’ whence the Modern English menses, meniscus (yet another crescent-shaped ‘little moon’), and semester (literally, ‘six months’). Associated with menses are its cousins menstruation, amenorrhea, menopause, and premenstrual syndrome. Goddess or gender studies might consider herein the nexus of a monthly cycle, the pull of the moon, madness, fertility, and ritual that runs deeply through the human experience. Long considered a kind of periodic, moon-induced insanity, mood swings and disorders associated with hormonal fluctuations were once treated by removing a woman’s reproductive organs: it’s no coincidence that hysterectomy and hysteria share a spelling, because they also share a meaning and an origin. One 1887 medical text explains that “It would have been as reasonable to extirpate the bed-sore of a sufferer from paretic dementia, and to cut off the hæmatomatous ear of a terminal dement, with the hope of curing his insanity thereby.” Although the practice was condemned as early as the 19th century, it continued at least into the 1980s in North America in a shameful example of medical madness. Now that’s crazy.

So, while moon and month share a common ancestry, few people would automatically associate them without prompting; the connection isn’t obvious to everyone. Germanic languages, including English, Dutch, and German, all have different but related words for ‘moon’ and ‘month,’ but most Romance languages diverge completely: Latin mensis gives us Spanish mes, Portuguese mês, and French mois, all meaning ‘month,’ but their words for ‘moon,’ luna, lua, and lune respectively,derive ultimately from Proto-Indo-European (PIE) base *leuk-, meaning ‘to light, shine,’ an etymon which also gives us light, translucent, luminous, illustrate, elucidate, illuminate, and luster, but also Lucifer, ‘light-bearer,’ an epithet for both Venus and Satan, and leukemia, named for white blood cells. All that glitters is not, apparently, gold.

Ultimately, many languages, though not all, differentiate lexically between ‘moon’ and ‘month;’ some have a word for moon from one historical base, meaning ‘light,’ and others from another historical base that is cognate to month. The PIE base *mēnes- is itself derived from *mē-, ‘to measure.’ Ayto tells us that “in ancient times the passage of time was measured by the revolutions of the moon.” This same ancient PIE base *me–yields measure, mete, meter, immense, meal (a ‘measure’ of food eaten at regular intervals), dimension, and commensurate. The presence of these two divergent etymologies for words that mean ‘moon’ speaks to the dual role of that heavenly body: it both measures and illuminates our world and how we perceive it.

Of course, people still try to make false and silly claims about the moon (the lunar perigee does not, for the record, cause tsunamis), as well as about the words that denote it (<month> is not, for the record, the base element of bimonthly). Such unscientific blunders, like surgical cures for hysteria, are an embarrassment to anyone who pursues real scientific inquiry. Can you imagine, for example, the data that early humans must have collected to determine just how the moon marked and was marked by time, how meticulous someone’s records must have been? It inspires me to think of how humans, in striving to understand the heavens, have leaned on the scientific principles of seeking patterns, weighing evidence, and always opting for the explanation that makes the fewest assumptions and accounts for the most examples.